#import "AssetCollection.h"
#import "Asset.h"
#import "ImageAsset.h"

@interface AssetCollection (Internals)
- (Asset *)assetForFilename:(NSString *)filename;
- (NSArray *)findAssetFilesInRootURL;
@end

@implementation AssetCollection

- initWithRootURL:(NSURL *)newRootURL {
    self = [super init];
    if (self) {
        rootURL = [newRootURL retain];
        assets = [[NSMutableArray alloc] init];
        previewImagePixelsPerSide = 80;
    }
    return self;
}

- (void)dealloc {
    [rootURL release];
    [assets release];
    [super dealloc];
}

- (NSURL *)rootURL {
    return rootURL;
}

- (NSArray *)assets {
    return [[assets retain] autorelease];
}

- (void)setAssets:(NSArray *)newAssets {
    if (assets != newAssets) {
        id old = assets;
        assets = [newAssets mutableCopy];
        [old release];
    }
}

- (void)insertObject:(id)obj inAssetsAtIndex:(NSUInteger)index {
    [assets insertObject:obj atIndex:index];
}

- (void)removeObjectFromAssetsAtIndex:(NSUInteger)index {
    [assets removeObjectAtIndex:index];
}

- (NSInteger)previewImagePixelsPerSide {
    return previewImagePixelsPerSide;
}

#pragma mark *** Background Update Control ***

- (void)refreshInBackgroundThread:(id)unusedObject {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    // Get a list of all the possible image files in root directory.
    NSArray *assetFiles = [self findAssetFilesInRootURL];

    // Identify three groups of image files:
    // (1) files that are in the catalog, but have since changed (the file's modification date is later than its last-cached date)
    // (2) files that exist on disk but are not yet in the catalog (presumably the file was added and we should create a catalog entry for it)
    // (3) files that exist in the catalog but not on disk (presumably the file was deleted and we should remove the corresponding catalog entry)
    NSMutableArray *assetsToProcess = [[self assets] mutableCopy];
    Asset *asset;
    NSMutableArray *assetsChanged = [NSMutableArray array];
    NSMutableArray *filesAdded = [NSMutableArray array];
    NSMutableArray *assetsRemoved = [NSMutableArray array];

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *rootPath = [[self rootURL] path];
    NSEnumerator *fileEnumerator = [assetFiles objectEnumerator];
    NSString *filename;
    while (filename = [fileEnumerator nextObject]) {

        // Get full path to file.
        NSString *path = [rootPath stringByAppendingPathComponent:filename];

        // Look for a corresponding entry in the catalog.
        asset = [self assetForFilename:filename];
        if (asset != nil) {
            // Check whether file has changed.
            NSDictionary *fileAttributes = [fileManager fileAttributesAtPath:path traverseLink:YES];
            if (fileAttributes != nil) {
                // Get file's modification date.
                NSDate *fileModificationDate = [fileAttributes objectForKey:NSFileModificationDate];
                if ([fileModificationDate compare:[asset dateLastUpdated]] == NSOrderedDescending) {
                    [assetsChanged addObject:asset];
                }
            } else {
                // NOTE: This shouldn't ever really happen, unless the file was deleted between our initial scan and getting to the file attribute check, but just in case, allow for the file to have been removed in that interval.
                [assetsRemoved addObject:asset];
            }

            // We've dealt with this catalogImage instance.
            [assetsToProcess removeObject:asset];
        } else {
            // File was added.
            [filesAdded addObject:filename];
        }
    }

    // Check for images in the catalog for which no corresponding file was found.
    [assetsRemoved addObjectsFromArray:assetsToProcess];
    [assetsToProcess release];
    assetsToProcess = nil;

    // Remove assets to be removed.
    NSEnumerator *assetEnumerator = [assetsRemoved objectEnumerator];
    while (asset = [assetEnumerator nextObject]) {
        [self performSelectorOnMainThread:@selector(removeAsset:) withObject:asset waitUntilDone:YES];
    }

    // Add assets to be added.
    fileEnumerator = [filesAdded objectEnumerator];
    while (filename = [fileEnumerator nextObject]) {
        NSURL *assetURL = [NSURL URLWithString:[filename stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding] relativeToURL:[self rootURL]];
        NSString *extension = [filename pathExtension];
        Asset *asset = nil;
        if ([[ImageAsset fileTypes] containsObject:extension]) {
            asset = [[ImageAsset alloc] initWithURL:assetURL];
        }
        if (asset != nil) {
            [self performSelectorOnMainThread:@selector(addAsset:) withObject:asset waitUntilDone:YES];
            [asset release];
            asset = nil;
        }
    }

    [pool release];
    inRefresh = NO;
}

- (void)startRefresh {
    if (!inRefresh) {
        inRefresh = YES;
        [NSThread detachNewThreadSelector:@selector(refreshInBackgroundThread:) toTarget:self withObject:nil];
    }
}

#pragma mark *** Main Thread Callback Points ***

- (void)addAsset:(Asset *)asset {
    [self insertObject:asset inAssetsAtIndex:[assets count]];
}

- (void)removeAsset:(Asset *)asset {
    NSUInteger index = [assets indexOfObject:asset];
    if (index != NSNotFound) {
        [self removeObjectFromAssetsAtIndex:index];
    }
}

@end

@implementation AssetCollection (Internals)

- (Asset *)assetForFilename:(NSString *)filename {
    // (Use of a dictionary or other more search-efficient construct would speed this up.)
    for (Asset *asset in [self assets]) {
        if ([filename isEqualToString:[asset filename]]) {
            return asset;
        }
    }
    return nil;
}

- (NSArray *)findAssetFilesInRootURL {
    NSString *rootPath = [[self rootURL] path];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSArray *possibleAssetFiles = [fileManager directoryContentsAtPath:rootPath];
    NSArray *supportedAssetFileTypes = [ImageAsset fileTypes];
    NSMutableArray *assetFiles = [NSMutableArray array];

    for (NSString *filename in possibleAssetFiles) {
        // (In a real-world application, if we have a filename with no extension, we should be prepared to check the file's HFS type code or other identifying metadata here.)
        if ([supportedAssetFileTypes containsObject:[filename pathExtension]]) {
            [assetFiles addObject:filename];
        }
    }
    return assetFiles;
}

@end

